As wireless communication systems such as cellular telephone, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication devices transmitting a growing volume of data with fixed resources. Traditional communication system designs employing a fixed resource (e.g., a fixed data rate for each communication device) have become challenged to provide high, but flexible, data transmission rates in view of the rapidly growing customer base and expanding levels of service.
The Third Generation Partnership Project Long Term Evolution (“3GPP LTE”) is the name generally used to describe an ongoing effort across the industry to improve the universal mobile telecommunications system (“UMTS”) for mobile communications to cope with continuing new requirements and the growing base of users. The goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards. The 3GPP LTE project is not itself a standard-generating effort, but will result in new recommendations for standards for the UMTS.
One of the areas addressed by the ongoing efforts is interference between cells in a wireless communication system. Interference coordination (also referred to as interference mitigation or interference control) is a generic term for any kind of system-level radio resource management-based interference mitigation scheme such as interference coordination and avoidance, inter-cell interference randomization, and inter-cell interference cancellation. Soft frequency reuse refers to one type of interference coordination scheme for evolved UMTS terrestrial radio access network (“e-UTRAN”) communication systems, which provides frequency coordination (or time-frequency coordination for synchronous systems) by applying power restrictions (reduced power) in certain time-frequency domains to achieve power coordination.
Within various interference coordination schemes in the 3GPP LTE project, power-sequence-based interference control, which is a soft frequency reuse interference coordination scheme, is the most commonly studied class of interference coordination schemes. In a soft frequency reuse-based interference coordination scheme, frequency (or time) resources are divided into different power level groups and an allocation procedure is utilized to divide the resources. In the allocation procedure, each sector is assigned portions of the frequency sub-bands according to a communication system plan, wherein different power constraints are assigned to different portions of frequency bands. Flexibility for interference reduction is achieved by varying power levels in the bands. Soft frequency reuse schemes can alleviate interference between cells because a fraction of the bandwidth in each cell is not used (affecting frequency reuse) and/or a penalty is not incurred because the fraction of the bandwidth in each cell is partially overlapped (as seen from the fractional frequency reuse schemes).
Proposals have been presented in the 3GPP LTE project for signaling to support adaptive interference control schemes that have focused on both a raw physical layer measurements point of view, such as the exchange of user equipment channel quality indicator measurements or pilot measurements between cells and radio resource management, and a quality-of-service point of view. While the proposals have addressed the interference coordination, there is still an opportunity for improvement therefor. Thus, considering the current limitations of communication systems including cellular networks, a system and method to manage interference between elements of a communication system to provide a higher level of communication reliability, particularly at the edge of the coverage area of a base station, that does not add substantially to signaling overhead and that is operable in real-time would be beneficial.
Accordingly, what is needed in the art is a system and method to self-optimize a level of interference between elements of a communication system in an interference coordination scheme. Advantageously, the reliability of handover signaling would thereby be increased. Otherwise, communication systems such as 3GPP LTE-compatible communication systems employing handover signaling may lose a competitive edge against other communication systems. Additionally, the system and method to self-optimize a level of interference between elements of a communication system to increase reliable handover should avoid inducing significant architectural changes to the existing communication systems.